The present invention relates generally to a method and apparatus for alignment and fixation of vertebral bodies.
Pedicle screws allow spine surgeons to attach rods or plates to the thoracic and lumbar spine. This rigidly immobilizes the spine segments, promoting the bone graft to grow into a fusion, welding spinal segments into one solid unit, reducing pain and stabilizing deformity without requiring complete immobilization of the patient for the extended period of time during the healing process.
While many different pedicle screws have been developed, presently most pedicle screws are fixed axis devices which must be carefully aligned during insertion and fixation in the spine. Specifically, the screws must be drilled or screwed into the bone at a very specific angle to assure that the alignment hardware is exactly positioned such that the receiving portions of the fixation hardware are aligned so that the rod can be passed therethrough without distorting the screw or putting an undesirable level of stress on the attachment point. As a result, the alignment procedure requires a considerable amount of time, increasing the possibilities of complications during surgery and, in many cases the alignment fails and must be repeated. Further, the insertion of the screw is dependent on the angle of alignment required, resulting in insertions that are not in the most secure or safe positions with respect to the vertebral bodies.
The art contains a variety of pedicle screws which permit a level of freedom with respect to the alignment of the screw and the coupling element. However, these teachings have generally been complex, and inadequately reliable with respect to durability. The considerable drawbacks associated with the prior art systems include limited angular adjustability, complexity, difficult of properly positioning the coupling elements and the rod, tedious manipulation of the many parts associated with the complex devices and the considerable cost associated with manufacturing such complex mechanisms.
Accordingly, a need exists for an inexpensive, durable and simple vertebral alignment assembly that allows a surgeon to freely manipulate the alignment of the coupling hardware such that the fixation rods can be properly positioned with respect to the vertebral bodies without a time consuming and potentially dangerous alignment procedure.
The present invention relates generally to a method and apparatus for aligning and fixing vertebral bodies. More specifically, the present invention is directed to a vertebral alignment/fixation assembly and method which allows a surgeon to manipulate and align the unit coupling the fixation hardware with the pedicle screw, the assembly comprising a hemispherical headed pedicle screw disposed within a slotted coupling unit designed to allow angular adjustment of the pedicle screw up to 90xc2x0 and which may be securely locked into position via a single threaded locking nut once a standard alignment rod has been inserted into the slotted coupling unit. The vertebral alignment/fixation assembly enabling the angular adjustment of the fixation system hardware after final placement and insertion of the pedicle screw into the vertebral body.
In one embodiment, the vertebral alignment/fixation assembly of the current invention generally consists of three main components: a hemispherical pedicle screw, a slotted coupling unit designed to receive the pedicle screw and an alignment rod, and a securing nut for fixing the angular position of the coupling unit and the position of the alignment rod within the coupling unit.
In one alternative exemplary embodiment, the pedicle screw of the invention has a slotted tip to allow the screw to self-tap the vertebral body and thereby ease the insertion of the screw into the bone.
In another exemplary embodiment the portion of the securing nut which engages the alignment rod is textured to provide a more secure grip of the alignment rod.
In still another exemplary embodiment the securing nut has an annular channel disposed such that a screw driver can be inserted therethrough and interact with the pedicle screw to drive the screw into a vertebral body.
In yet another exemplary embodiment the pedicle screw is provided with a square opening in its hemispherical head such that a square headed driving tool can be mated therewith to drive the screw into the vertebral body.
In still yet another exemplary embodiment the components of the system are made from an orthopaedically suitable material, such as, for example, stainless steel or titanium.
In still yet another preferred embodiment, the invention is directed to a system for aligning and fixing vertebral bodies comprising a multiplicity of vertebral alignment components as described above attached at suitable points of attachment as determined by the deformity of the spine.
In still yet another embodiment, the invention is directed to a method for aligning vertebral bodies. The method comprises manipulating, aligning and fixing the spine using a vertebral alignment system as described above.